1. Field of the Invention
The present invention relates generally to a speech recognition system for an automotive vehicle, and more particularly to a speech recognition system by which a plurality of similar spoken instructions including the same phrase can be recognized separately, without repeating the same phrase, in order to improve the recognition rate.
2. Description of the Prior Art
There is a well-known speech recognizer which can activate various actuators in response to human spoken instructions. When this speech recognizer is mounted on a vehicle, the headlight, for instance, can be turned on or off in response to spoken instructions such as "Headlight on" or "headlight off". Such a speech recognizer usually can recognize various spoken instructions in order to control various actuators; however, there are some problems involved in applying this system to an automotive vehicle.
In an automotive vehicle, it is desirable to actuate various equipment or devices such as head lights, wipers, a car-radio, fender mirrors, door windows, etc. by the use of a speech recognition system. These automotive vehicle mounted devices can be classified into two groups from the standpoint of operation modes. One group includes on-off type devices such as head lights, wipers, window washers, car-radio, etc., which are simply turned on or off; the other group includes adjustable-type devices such as fender mirrors, door windows, etc. For instance, in the case of the fender mirrors, it is necessary for the driver to adjust one or both of the right-hand and left-hand fender mirrors and further adjust it in one or both of the horizontal and vertical directions in which the mirror is moved for adjustment. In the case of the door windows, the driver must open or close one or both of the right-hand and left-hand door windows. Further, in the case of driver seats, there are two seats such as a driver seat or a passenger seat, and the driver must determine the operation modes to move the seat frontward or rearward or to tilt the seat back frontward or rearward.
In the case where the devices having two or more operation modes are required to be adjusted with a speech recognizer, the driver usually actuates the device in an operation-mode sequence. In the case of fender mirrors, for instance, the right-hand mirror is first adjusted in the horizontal direction and then in the vertical direction. Thereafter, the left mirror is adjusted in the horizontal direction and then in the vertical direction. In the case of a seat, the seat is moved frontward and then the seat back is tilted backward. In the case of door windows, the right window is opened and then the left window is opened.
Therefore, for instance, in the case where the fender mirrors are adjusted, four instruction phrases, namely "Right-mirror, horizontally", "Right-mirror, vertically", "Left-mirror, horizontally" and "Left-mirror, vertically" must be recorded and recognized by the speech recognizer sequentially.
In order to reduce the capacity of a memory unit in the recording mode, there has been proposed a method wherein spoken instructions indicative of the kinds of devices to be actuated (referred to as "device instruction phrases") such as "Mirror" and spoken instructions indicative of the kinds of operation modes to be adjusted (referred to as "operation-mode instruction phrases") such as "Right, horizontally" or "Right, vertically" are recorded separately and recognized independently, because an instruction phrase "Mirror" is common to the spoken instructions. In the method as described above, it is possible to reduce the capacity of a memory unit for each instruction phrase, thus improving the recognition rate since the length of each instruction phrase is short. The reduced capacity is possible even though the total number of instruction phrases to be recorded in the speech recognizer increases in the spoken instruction recording mode.
In the prior-art method in which device insruction phrases and operation-mode instruction phrases are recorded separately in the recording mode, since all the instruction phrases "Mirror, right, horizontally", "Mirror, right, vertically", "Mirror, left, horizontally", and "Mirror, left vertically" must be supplied sequentially to the speech recognizer in the recognition mode, it is very troublesome to say the similar spoken instructions repeatedly. Additionally, since the system must recognize similar sequential spoken instructions, there is a danger of misrecognition.
A more detailed description of a typical speech recognizer will be made with reference to the attached drawings in conjunction with the present invention under DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS.